The present invention relates to hand stamps. A marking structure is an article having a pattern formed thereon for use in printing an ink onto a printable surface. A marking structure is sometimes referred to as a “stamp die” or a “stamp text plate”.
Microporous marking structures for use with hand stamps are typically made of a polymeric material, or other open cell compositions, such as specially formulated foam, and resin, such as thermoplastic resin, which combine to form a slab-like structure including a large quantity of microscopic pores. The microporous structure may be impregnated with ink or other suitable marking fluid, which fill many of the microscopic pores.
Hand stamps having microporous marking structures are commercially known as pre-inked hand stamps as they can be used to create numerous impressions without requiring a user to introduce additional ink into the marking structure. This is possible due to the microscopic size of the pores, which allow the ink initially retained therein to escape at a controlled rate.
One high quality, pre-inked hand stamp is manufactured and sold under the trademark ROYAL MARK by M&R Marking Systems Inc. of Piscataway, N.J. These pre-inked hand stamps include marking structures made using a gel comprising a mixture of thermoplastic resin and ink, which is commonly referred to as a pre-mix.
There are a variety of methods for manufacturing microporous marking structures. In one method, the pre-mix, which includes a desired quantity of ink, is poured into a mold. The mold is then heated in a vulcanizer at a predetermined pressure and temperature for a selected period of time. When the pressure, temperature and time parameters have been satisfied, the marking structure is formed into a microporous slab. The marking structure is then removed from the mold and any excess ink in the structure is removed during a stabilizing process. The marking structure has a resilient microporous network that contains ink, which is released through protruding indicia of a molding when pressed against a surface to be marked.
Another well known method of manufacturing microporous marking structures includes initially forming a microporous structure that does not contain ink. Such microporous marking structures may be manufactured by sintering, salt-leaching or other methods. This type of microporous marking structure is impregnated with ink during a separate procedure which may involve immersing the microporous marking structure in an ink pool, subjecting the microporous marking structure and ink to a vacuum environment or other known methods. With this type of microporous marking structure, it is generally necessary to stabilize the structure, i.e. remove excess ink therefrom, prior to assembly of the marking structure on a hand stamp mount.
Another type of pre-inked stamp uses a microporous foam upon which an image is flash printed. One flash exposure system for manufacturing pre-inked hand stamps is described at M&R Marking System Inc.'s Website at www.mrmarking.com and is provided under the trademark ULTIMARK. In general, the ULTIMARK system comprises a computer controlled flash irradiation device which exposes select areas of foam text plates (i.e. marking structures that have been formulated to be used in pre-inked hand stamps) to a high energy light source for a period of time. A protective film is used to shield certain areas of the microporous foam so that the shielded areas are not exposed to the light source. The brief exposure to light causes the exposed surfaces of the text plate to melt creating substantially non-porous areas at the exterior surfaces of the microporous foam. The unexposed areas remain porous so that the microporous foam can be subsequently used as a marking structure in hand stamps.
In one particular embodiment of the ULTIMARK system, the flash-exposed pre-inked stamps are made by printing or imaging a positive or negative image on a transparent paper or plastic, and then placing that image on a transparent body of typically glass or plastic in between a light source and the microporous foam to be exposed. A clear protective sheet may be placed over the flash exposable microporous material and on top of a transparent indicia medium. A process for preparing a microporous material for flash exposure is disclosed in commonly assigned U.S. patent application Ser. No. 10/439,469, now U.S. Pat. No. 7,166,395, the disclosure of which is incorporated herein by reference.
There have been a number of efforts directed to producing ink stamps capable of printing in two or more colors. For example, U.S. Pat. No. 6,239,806 to Hirano describes a stamp having “stamping material” (i.e. the stamping part) which has a continuous porous structure for holding and releasing ink through patterns on the stamping face thereof to imprint an object. The continuous porous stamping material is fed from the back side by a separate occlusion body (i.e., an ink reservoir) having two or more sections for holding inks of different colors. While the reservoir has a physical barrier and/or an isolation part (e.g., a space) for keeping the inks separate, the continuous porous stamping material has neither barrier nor physical separation between portions filled with different inks. Hirano further describes the inks themselves as “becom[ing] a physical barrier” when the stamping material is simultaneously filled with ink, in that “each ink does not excessively penetrate out of each desired area.” (col.10, 11.8-10)(Emphasis added) It is clear from the above description that Hirano neither teaches nor suggests any barrier in the stamping material itself for preventing the different inks from migrating between respective portions and mingling with each other.
U.S. Pat. No. 6,047,639 to Shih discloses a stamping set including at least one partition strip that separates an enclosed space into at least two rooms for separating ink of two different colors. Although the '639 patent also addresses the issue of preventing color mingling, it also requires the use of an additional component, i.e. a partition strip.
U.S. Pat. No. 5,601,644 discloses a multi-color ink stamp pad, whereby a thin, aqueous-impermeable film is disposed between the pads for preventing color mingling. Thus, the '644 patent also requires an additional part to prevent mixing of the different colored inks.
There have also been a number of efforts direct to simplifying assembly of hand stamps. For example, U.S. Pat. No. 3,988,987 to Ikura discloses a stamp frame having a vertical interlocking projection on one of its side surfaces, a vertical interlocking groove on the opposite side surface, and a holding member removably mountable over the stamp elements to prevent displacement of the stamp elements relative to one another. Although Ikura applies to ensuring proper assembly of a stamp device, it teaches a registration concept applied to a stamp frame rather than the stamp pad itself. As such, there is nothing in the disclosure indicating a registration concept on the adjacent portions of the marking structure to facilitate the assembly of marking structures on a hand stamp mount.